Multi-function starch compositions

ABSTRACT

The invention relates to a dry mix composition comprising a starch component and a papermaking additive, particularly an uncooked starch component and a heat sensitive papermaking additive. The dry mix can be added to water to form a slurry. The invention further concerns the application of the slurry to a paper mat in paper manufacturing and a process for making the dry mix composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates compositions comprising a starch component andpapermaking additives, particularly heat sensitive papermakingadditives. The invention further relates to the application of thecompositions to a paper mat at the wet end of the papermaking process, amethod for applying the composition to the paper mat by spraying and aprocess for making the composition.

2. The Related Art

Additives are generally used in making paper and board to providedesired properties to the paper and board. In some papermaking processesthe additives are applied to the paper or board with cooked starch. Thisis particularly the case with additives having small particle sizes. Theuse of cooked starch and additives provides a colloidal suspension whichfacilitates uniform distribution of the additive in the paper product.

Colloidal suspensions of cooked starch and additive can be used in thepaper pulp or for a coating. U.S. Pat. No. 4,264,325 describes anexample wherein an optical brightening agent is worked into a colloidalsolution of cooked starch and water which is used as size liquor andcoated onto paper prior to drying.

Certain papermaking additives, however, are sensitive to heat. Theseheat sensitive papermaking additives will lose some or all of theireffectiveness and/or function when heated at elevated temperatures. Whenthe papermaker desires to use a colloidal suspension of cooked starchand heat sensitive papermaking additives, the papermaker must cook thestarch prior to incorporating the heat sensitive additive in thecolloidal suspension to avoid losing effectiveness and/or function ofthe additive. This requires the papermaker to operate and maintainequipment to cook starch as part of the papermaking process.

A composition comprising uncooked starch and heat sensitive papermakingadditives which can be applied to paper within the papermaking processwithout prior cooking of the starch, yet provide the benefits of the useof a colloidal suspension of cooked starch and heat sensitivepapermaking additive, would be desired in the art. A method for applyingthe uncooked starch and heat sensitive papermaking additives thatprovides the benefits of application of cooked starch and heat sensitivepapermaking additive without prior cooking of the starch would also bedesired.

In the present Specification, all parts and percentages are on aweight-by-weight basis unless otherwise specified. “By weight based onthe uncooked starch component” means the total amount of a particularcomponent of the composition per the total amount of uncooked starch inthe composition.

SUMMARY OF THE INVENTION

The invention pertains to a composition comprising an uncooked starchcomponent and papermaking additive, particularly a heat sensitivepapermaking additive. The uncooked starch component and heat sensitivepapermaking additive are dry blended. When used in the papermakingprocess, the composition is slurried with water and applied to the paperwithout cooking the starch component. After application, the paper maybe heated which will cook the starch component; however, we have foundthat the heat sensitive papermaking additive is not adversely affected(e.g., does not lose significant, if any, effectiveness and/orfunctionality) by heating with the uncooked starch in the papermakingprocess, e.g., after being applied to the paper mat.

The invention further relates to a method for applying the compositioncomprising the uncooked starch component and the heat sensitivepapermaking additive to the paper after the paper mat is formed. Theuncooked starch component and papermaking additive can be sprayed ontothe paper mat after the mat exits the head box. This type of spraymethod is described with respect to the application of starch and fibermixtures in the co-pending application owned by the assignee, U.S.patent application Ser. No. 10/712,699, filed Nov. 12, 2003 entitled“STARCH AND FIBER MIXTURE FOR PAPERMAKING AND METHODS OF MAKING PAPERWITH THE MIXTURE”, which is incorporated by reference herein in itsentirety.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing a papermaking process comprising theapplication of the uncooked starch and heat sensitive papermakingadditive to a paper mat.

FIG. 2 is a graph showing brightness gained from an optical brighteningagent (y-axis) vs. amount of optical brightening agent in a handsheet(x-axis) where uncooked pearl starch and optical brightening agent aresprayed onto the surface of a paper mat.

DETAILED DESCRIPTION OF THE INVENTION

The composition comprising the uncooked starch component and heatsensitive papermaking additive composition comprises from about 90% toless than 100%, by weight, of an uncooked starch component and betweenmore than zero to no more than about 10%, by weight, of a heat sensitivepapermaking additive. When combined with water in the form of a slurry,the slurried composition comprises from about 0.01% to about 20%, byweight, uncooked starch component and about 0.01% to about 10%, byweight of the uncooked starch component, of one or more heat sensitivepapermaking additives. The slurried composition may comprise about 8% toabout 12%, by weight, uncooked starch component and about 0.1% to about5%, by weight of the uncooked starch component, of one or more heatsensitive papermaking additives. The dry mix and slurried compositionmay also comprise other papermaking additives that are not considered tobe heat sensitive papermaking additives. The dry mix may consistessentially of or consist of uncooked starch and heat sensitivepapermaking additives.

Both natural unmodified starch and modified starch can be used for theuncooked starch component in the composition, each providing equal orabout equal performance. Modified starches may also be used as a drystrength agent in the heat sensitive papermaking additive component ofthe invention. Any starch appropriate for use in papermaking may be usedand dextrin, as well as combinations of starch types, dextrin types andcombinations of starches and dextrins. Also, maltodextrins and otherforms of carbohydrates can be used as the starch component. The uncookedstarch component comprises material selected from the group consistingof unmodified starch, modified starch, dextrin, maltodextrin andcombinations thereof.

Unmodified starch is a commodity chemical produced from the root, stemor fruit from a number of plants. It is a high molecular weightcarbohydrate polymer which is comprised of linear and branchedpolysaccharide polymers and it can have moisture content from about 8%to about 20%, most commonly from about 11 % to about 13%. Starches suchas those derived from corn, wheat, barley, tapioca, rice, potato and/orother suitable plant source, and the like can be used, as well ashybrids. Blends of starches from various sources also can be used. Pearlstarches and powdered starches may be used.

Modified starch can be mechanically, chemically or heat modified.Modified starches have different properties than unmodified starch,including differences in solubility, film forming, whiteness, gelstrength, viscosity stability, adhesivity, resistance to shear andresistance to freeze-thaw degradation. Starches derived from othergenetic forms of corn, such as high amylose and waxy corn, as well assorghum varieties, would also be suitable. Chemically modified starchesuseful in the invention include modified oxidized starch such ashypochlorite-oxidized starch, acid thinned starches, cross-bondedstarch, etherified starches, esterified-starches and others which havereduced molecular weight, high fluidity and/or functional sub groups.Examples of chemically modified starches which can be used in theinvention and are commercially available are SUREBOND® Industrial CornStarch or STABLEBOND® Industrial Corn Starch available from CornProducts International, Inc., Westchester, Ill., USA (“Corn Products”.FOXHEAD® Cationic Starches available from Corn Products and CornProducts' oxidized starch may also be used in the invention.

The heat sensitive papermaking additive may be selected from the groupconsisting of optical brightening agents, fluorescent agents, drystrength agents, filler particles, sizing agents, flame retardants,pigments and combinations thereof. Optical brightening agents that maybe used in the invention include BLANKOPHOR® UW liquid and otherBLANKOPHOR® optical brightening agents, available from Bayer Chemicals,Pittsburgh, Pa., USA and optical brightening agents from ClariantCorporation, Charlotte, N.C., USA available under the trade nameLEUCOPHOR®. Sizing agents useful in the invention include BASOPLAST®available from BASF Corporation, Mount Olive, N.J., USA. Useful flameretardants include SAFE-T-GUARD® available from FireTech Co., CanyonCountry, Calif., USA, and useful dry strength agents include theFOXHEAD® modified starches from Corn Products. Pigments includeconventional pigments as well as pigment types such as solid sphereplastic pigments and hollow sphere plastic pigments, which arecommercially available, such as hollow sphere pigments from DowChemical, Midland, Mich., USA.

The dry mix composition comprising starch and heat sensitive papermakingadditive may be made by dry blending the uncooked starch component andheat sensitive papermaking additive. In one method for making the drymix, the heat sensitive papermaking additive, and other optionaladditives, is added in liquid form into a pneumatic conveyance line. Theliquid droplets are atomized as they enter the conveyance line fordrying. The starch is blown into the pneumatic conveyance line and comesinto contact with the heat sensitive ingredient after the heat sensitiveingredient, and other optional additives, is atomized in order to dryblend the components. The flow rate of the starch in the pneumaticconveyance line will determine the rate of addition of heat sensitivepapermaking additive in the pneumatic conveyance line. In an embodimentof the invention, the air pressure in the pneumatic line is about 60 psi(about 4.2 kg/cm²) to about 100 psi (about 7.1 kg/cm²).

The composition is made up for use at the papermaking facility by addingthe uncooked starch component and heat sensitive papermaking additivecomposition to water to form a slurry. The slurry is made byconventional means that would be understood by one skilled in the art.Generally, the slurry is made by adding the composition to water so thata homogenous slurry is obtained. The uncooked starch component and heatsensitive papermaking additives are mixed with water in sufficientquantities and for sufficient time to thoroughly wet out the starch. Thedry mix of uncooked starch component and heat sensitive papermakingadditive is mixed with water in any type of mixing apparatus at atemperature, such as ambient temperature, so that the starch is notcooked during the slurrying process.

The slurry comprising the uncooked starch component and heat sensitivepapermaking additive can be applied as a coating to the paper byconventional means. The slurry can be applied to a surface of a papermat, having a top surface and a bottom surface, during the papermakingprocess. For example, the uncooked starch component and heat sensitivepapermaking additive slurry can be applied with spraying systems, aswell as with spray bars, curtain coaters, blade coaters, rod coaters,air knife coaters, roll coaters, size presses, and the like.

In an embodiment of the invention, the slurry of the uncooked starchcomponent and heat sensitive papermaking additive is sprayed onto asurface of the paper mat at the wet end of the papermaking process, suchas prior to the nip of the press section. A papermaking processcomprising means for applying the uncooked starch component and heatsensitive papermaking additive using spraying is shown in FIG. 1. A pulpand process water stream 1 is sent to a head box 2 by a first means forcirculation 3 such as a pump, and the head box 2 deposits the pulp andprocess water onto the wire screen 4 where the paper web or mat 6,having a top surface 6 a and bottom surface 6 b, is formed. The pulp andprocess water is filtered through the mat forming the white water 5which is collected in a tray 7 and recycled through the system with orwithout further processing.

Referring again to FIG. 1, the slurry of the uncooked starch componentand heat sensitive papermaking additive is made up in a mixer 8 and sentto a means 9 for applying the slurry of the uncooked starch componentand heat sensitive papermaking additive to the paper mat 6, such as asurface of the paper mat like the top surface 6 a. A spray bar or spraynozzle may be used as the means 9. As shown in FIG. 1, the slurry may besent through a means for separation 10, such as a filter or pressurescreen to remove any large particles, e.g., starch contaminants. Filtersavailable from RPA Process Technologies USA, Portage, Mich., USA may beused. The filter must be properly sealed to prevent pressure drop,particularly during the cleaning cycle, to provide continuous flow tothe means 9 for applying the slurry of the uncooked starch component andheat sensitive papermaking additive to the paper mats. The accepts 11from the means for separation 10 are sent to the means 9 for applyingthe uncooked starch component and heat sensitive papermaking additiveslurry and the rejects 12 are discarded. The uncooked starch componentand heat sensitive papermaking additive slurry is applied to the papermat 6 after the mat is formed on the wire screen but before the papermat is further processed (shown graphically as block 13 in FIG. 1) suchas by drying and pressing, like prior to the nip of the press section.

During the application method, the uncooked starch component and heatsensitive papermaking additives permeate through the paper mat (e.g.,move through the paper mat from the top surface to the bottom surface)such that at least some of the slurry permeates to the bottom surface ofthe paper mat. In this manner, the uncooked starch and heat sensitivepapermaking additive becomes absorbed in the paper mat. The uncookedstarch component prevents the heat sensitive papermaking additive fromcompletely running through the paper mat. The uncooked starch componentalso uniformly, or substantially uniformly, distributes the heatsensitive papermaking additive within the paper mat and, thus within thefinished paper product at the end of the papermaking process.

During the process for drying the paper mat, the starch component iscooked and gelatinizes, however, because the drying process does notprovide as much direct heat to the heat sensitive papermaking additiveas would occur if the combination of the uncooked starch component andheat sensitive papermaking additive were directly heated to cook thestarch, the heat sensitive papermaking additive ingredient is notnegatively affected during the heating process and does not loose any orsignificant effectiveness and/or function. The papermaker achieves thebenefits of the combination of a cooked starch component and apapermaking additive without the need to separately cook the starchbefore adding a heat sensitive papermaking additive. The papermaker doesnot need to maintain equipment for cooking the starch and can eliminatea separate starch cooking step in the papermaking process.

EXAMPLE 1

Handsheets of paper were made from 100% softwood fibers that wererefined in a valley beater (lab/pilot scale) from Voith Sulzer,Appleton, Wisc., USA to about 400 Canadian Standard Freeness (“CSF”).The brightness of the handsheets, without application of an uncookedstarch component and optical brightening agent composition, wasdetermined to be 75.6 using a Micro S5 brightness/opacity/color meterfrom Technidyne Corporation, New Albany, Ind., USA using the testingprocedures described in the operations manual for the Micro S5 meter.

A 15% starch slurry was dosed with 5 grams optical brightening agent(BLANKOPHOR® UW liquid from Bayer Chemicals) per 1000 grams of starch(3005 Pearl Starch from Corn Products). This slurry was thoroughly mixedand applied to handsheets (made as described above) using a VEEJET® 8006spray nozzle from Spraying Systems Co., Wheaton, Ill., USA at 275.78kilopascal (40 psi). The spray nozzle was swept back and forth acrossthe handsheets (making 2 passes in about 1 second) as soon as the levelof the water dropped below the forming screen of the handsheet mould.Two sheets of blotter paper and a roll were then used to press thehandsheets. The outer sheet of the blotter paper was then discarded. Thehandsheet and remaining blotter paper were then placed in the press feltand run through the roll press. The felt and blotter paper were removedand the handsheet alone was run through the roll press a final time. Thehandsheets were twice run through the roll dryer at 115.56° C. (240° F.)to cook the starch and dry the handsheet.

A 15% starch slurry was dosed with 10 grams of optical brightening agent(BLANKOPHOR® UW liquid from Bayer Chemicals) per 1,000 grams of starch(3005 Pearl Starch from Corn Products). This slurry was applied to ahandsheet and the handsheet was finished and dried in accordance withthe procedure discussed above with respect to the 5 gram dose.

The handsheets having the 5 gram and 10 gram dosages of opticalbrightening agent were allowed to condition for a minimum of 24 hours,and were then tested for brightness using the testing proceduresdescribed in the operations manual for the Micro S5 meter fromTechnidyne Corporation. Results for brightness are set forth in Table 1.FIG. 2 provides a graph of the brightness gained in the handsheet as aresult of the addition of optical brightening agent, based on theaverage brightness of 75.6 for sheets made from the same pulp as thosein the example, but without having the uncooked starch and opticalbrightening agent slurry sprayed on the sheet. TABLE 1 Optical OpticalBrightening Brightening Agent Agent Brightness (5 grams) (10 grams) UVincluded 80.44 82.58 UV excluded 76.37 76.21 FL comp 4.08 6.38

In Table 1, “UV (ultra Violet) included” is the brightness of the paperwhen exposed to a light source that contains a fluorescent component.“UV excluded” is the brightness of the sample when exposed to a lightsource that has no UV radiation. “FL Comp” is the amount of brightnessadded by the inclusion of UV light to the sheet (the difference betweenUV Included and UV Excluded).

1. A method of applying heat sensitive papermaking additives to paperduring a papermaking process comprising the steps of a) providing a drymix comprising an uncooked starch component and one or more heatsensitive papermaking additives; b) adding the dry mix to water to forma slurry without cooking the starch; c) providing a paper mat having atop surface and a bottom surface; d) applying the slurry to the topsurface of the paper mat and allowing at least some of the slurry topermeate to the bottom surface of the paper mat; and e) heating thepaper mat after applying the slurry to cook some or all of the starch.2. The method of claim 1 wherein the slurry comprises the uncookedstarch component in an amount of from about 0.1% to about 20%, byweight, and about 0.01% to about 10%, by weight of the uncooked starchcomponent, of the heat sensitive papermaking additives.
 3. The method ofclaim 1 wherein the heat sensitive papermaking additives are selectedfrom the group consisting of optical brightening agents, fluorescentagents, dry strength agents, filler particles, sizing agents, flameretardants, pigments and combinations thereof.
 4. The method of claim 1wherein the uncooked starch component is selected from the groupconsisting of unmodified starch, modified starch, dextrin, maltodextrinand combinations thereof.
 5. The method of claim 4 wherein theunmodified starch or modified starch are derived from a source selectedfrom the group consisting of corn, wheat, barley, tapioca, rice, potatoand combinations thereof.
 6. The method of claim 4 wherein theunmodified starch or modified starch is pearl starch.
 7. The method ofclaim 1 wherein the slurry is applied to the paper mat by spraying theslurry onto the top surface of the paper mat with a spray bar.
 8. Themethod of claim 1 wherein the slurry is applied to the paper mat byspraying the slurry onto the top surface of the paper mat with a spraynozzle.
 9. The method of claim 1 wherein the slurry is applied to thepaper mat by means selected from the group consisting of curtaincoaters, blade coaters, rod coaters, air knife coaters, roll coaters andsize presses.
 10. The method of claim 1 wherein the paper mat is formedby sending pulp and process water to a head box, having the processwater deposited from the head box onto a wire screen and removing thepaper mat from the wire screen.
 11. The method of claim 10 wherein theslurry is applied to the paper mat after the paper mat is removed fromthe wire screen.
 12. A process for making paper comprising the method ofclaim
 1. 13. A process for making paper comprising the method of claim10.
 14. Paper made by the process of claim
 12. 15. A dry mix compositionthat can be applied to a paper mat in the form of a slurry fordistribution of one or more heat sensitive papermaking additives withinthe paper mat comprising from about 90% to less than 100% of an uncookedstarch component and between more than zero to no more than about 10% ofa heat sensitive papermaking additive.
 16. The composition of claim 15wherein the heat sensitive papermaking additives are selected from thegroup consisting of optical brightening agents, fluorescent agents, drystrength agents, filler particles, sizing agents, flame retardants,pigments and combinations thereof.
 17. The composition of claim 15wherein the uncooked starch component is selected from the groupconsisting of unmodified starch, modified starch, dextrin, maltodextrinand combinations thereof.
 18. The composition of claim 17 wherein theunmodified starch or modified starch are derived from a source selectedfrom the group consisting of corn, wheat, barley, tapioca, rice, potatoand combinations thereof.
 19. A paper mat comprising a slurry of the drymix composition of claim 15 and water.
 20. A process for making a drymix composition comprising the steps of blowing starch into a pneumaticconveyance line having an air pressure of about 60 psi to about 100 psiand adding heat sensitive papermaking additive and optional additive inliquid form into the pneumatic conveyance line wherein the heatsensitive papermaking additive and optional additive are atomizied asthe heat sensitive papermaking additive and optional additive enter theconveyance line.